Fluid motor-pumping means which include a pair of axially aligned cylinders add interconnected pistons therein are well known as shown, for example, in U.S. Pat. Nos. 4,637,783, issued Jan. 20, 1987; 3,649,136, issued Mar. 14 1972; 3,540,873, issued Sept. 29, 1970; 421,159, issued Feb. 11, 1890; 3,234,746, issued Feb. 15, 1966; 3,825,122, issued July 23, 1974; 3,700,360, issued Oct. 24, 1972; 4,367,140, issued Jan. 4, 1983; 3,349,995, issued Oct. 31, 1967; and 2,816,822, issued Dec. 17, 1957. A similar fluid motor-pumping means is shown in United Kingdom patent No. 1,176,531 published Jan. 7, 1980. In many of the above-identified systems, the valving arrangement for control of fluid to and from the motor-pumping means is located separately from the cylinders and is subject to loss of fluid in the event of leakage past the valves. Also, many of the arrangements have no provision for storing and returning kinetic energy of the pistons and/or means for minimizing the harmful effects of water hammer.